An improved method for preparing a frozen food product is provided. The food product comprises a variety of food pieces that have been precooked in the presence of water and subjected to a process in which substantially all of the free water present with the food pieces is removed. The food pieces are then passed through a continuous freezing unit which increases the rigidity of the food pieces and leaves an amount of water on the surfaces of the food pieces. The food pieces are placed into a heat sealable container that includes a porous end piece along with measured amounts of a freezing gas and an adjuvant. The container is then sealed across the porous end piece and placed on a tumbling mechanism that coats the food pieces with the adjuvant and completes the freezing process as the freezing gas escapes through the porous end piece on the container. After completion of the tumbling process, the containers are resealed beneath the porous end piece so that the porous end piece may be trimmed from the container, allowing the container to be packaged and shipped for sale.